The Malthusian theory was once thought to be, pretty much, relegated to the status of a curious footnote in the history of economic thought.Henry George's chapters on poverty and subsistence instand as the definitive marshalling of the abundant logical ammunition against it. D., however, an influential crew of neo-Malthusians brought the theory back.
Also, modern Malthusians such as Paul Ehrlich, Lester Brown and the happy fun guys that called themselves the Club of Rome have added a wrinkle, claiming that subsistence can keep ahead of population growth at the cost of an unsustainable level of envronmental harm.
Seven billion people is a lot of people, no doubt about it. The neo-Malthusian view seems reasonable, especially when fortified by such statistics as these (published by the Population Institute): These charts show one of the most troubling trends in world demographics.
Two factors consistently correlate with high birth rates: poverty, and poor education.
It has long been known that when living standards rise in a community, birth rates tend to decline; this widely-documented phenomenon is called the "demographic shift" (Henry George referred to it in 1879).
and originator of the perception of economics as "the dismal science." Malthus reasoned that human population tends to grow at a geometrical rate, while our ability to prooduce subsistence increases at a merely arithmetical rate and so we find ourselves in an ever-deepening spiral of suffering caused by overpopulation.
In Malthus's view this process could only be slowed by the "preventive check" of decreased fertility (presumably attained through zealous spiritual devotion) or, the "positive check" of increased mortality.
In Brazil, for example, the situation became so acute that squatters have been massacred for occupying remote, unused areas of privately-held ranches.
A large, organized movement has grown around the peasants' demand simply to be allowed to use land that others don't feel like using, just now.
Ever-increasing numbers of people in the worlds poorest areas are moving into cities.
This has placed great pressures on already-troubled nations.